As described in the parent hereto, rotational viscometers require a rotating element called the rotor and a stationary element in fluid contact with the rotor which is called the stator. Usually, particularly in sensitive rotational viscometers such as the Brookfield viscometer, the rotor, which is driven by the Brookfield head, is immersed in a large container of liquid. In some applications such as in the well-known Scanning Brookfield Technique, developed by Mr. Theodore W. Selby and licensed to the Tannas Co., Midland, Mich., used in ASTM D 5133, and improved by a support and centering device disclosed by Deysarkar et al., U.S. Pat. 4,648,263, and in the parent hereto, the rotor must be relatively close to the stator wall to gain the necessary sensitivity. In such a case, the rotor must be centered very carefully.
In practice, problems are encountered with the commercially available support and centering attachment of Deysarkar et al., which is known commercially as the Pennzoil/Tannas rotor/stator centering adapter, Tannas Model SBV-P. In particular, and in reference to the foregoing patent, an O-ring, present in the SBV-P adapter in a slot cut in interior surface 54 of cylindrical member 70, can swell as from contact with solvents or oil to the point where sometimes, upon the contraction of the constraining cylindrical member 70, a glass stator 28 may break. The O-ring also may become worn or oily, and, if a loose fit between cylindrical member 70 and stator 28 is engendered, slippage and rotation of the stator occurs during testing, which destroys the value of the test. Furthermore, the O-ring can be difficult to install and remove for replacement. Another effect of low-temperature contraction of cylindrical member 70 is that, when bath 44 controls the test liquid temperature at minus 40 degrees C., or below, separation of parts of device 40, to include removal of a glass stator 28 filled with tested liquid from the lower end 52 of the device, becomes very difficult because of the aforementioned contraction of the engineering thermoplastic employed to make the adapter. Other problems exist, in particular with the device disclosed by Deysarkar et al.
What is needed is another adapter which overcomes such problems while providing for precise centering of the rotor spindle in the stator of a sensitive rotating viscometer. The adapter should be readily manufacturable--and be efficient to operate, especially by even inexperienced operators.